Electronic circuits that are supplied during normal operation with supply voltages that are higher than usually acceptable voltages for its internal components, such as complementary metal oxide semiconductor (CMOS) or bipolar switching devices, may experience transient operational conditions during which the acceptable voltages at its internal components are temporarily exceeded. This causes stress to the internal components since the safety operation area (SOA) of the electronic circuit is at least temporarily left. Repeated and prolonged remainder outside the SOA of an electronic circuit may have a negative impact on the reliability, lifetime and accuracy of the circuit.
U.S. Pat. No. 6,917,554 discloses a protection circuit for internal nodes of a flash EEPROM chip from a power pad. The protection circuit is able to maintain the node voltage at the internal nodes at a predetermined voltage level by means of diode connected devices and a current bleeding path.
U.S. Pat. No. 6,940,336 discloses a voltage regulator with switch-on protection circuitry that initially blocks an output transistor of the regulator while an input voltage rises during start-up and that enables the output transistor of the regulator after lapse of a start-up guard period.
U.S. Pat. No. 5,319,601 discloses a power supply circuit for a DRAM with a power-on detection circuit which detects when an external power supply potential reaches a predetermined potential. An internal power supply circuit further has two intermediate potential generating circuits of which the one with the larger driving capability is only initially activated during a ramp-up period of the external power supply potential.
However, a disadvantage of the above circuits is that they do not sufficiently protect electronic circuitry that is supplied with an external supply voltage from overvoltage.